Fe Wire-Based Metal–Organic Frameworks for Advanced Gas and Vapor Adsorption: Effect of Functional Compatibility on Hierarchical Pore Diffusivity and Atomic Simulation Insights

This study introduces a novel method for synthesizing a Fe-based metal-organic framework (MOF), leveraging Fe wire as a substrate and an iron precursor source with which to grow MIL-88B(Fe) and MIL-88B(Fe)-NH₂. This simple in situ approach requires only the addition of a ligand precursor for MOF formation, eliminating the need for an additional metal precursor. The adsorption performance of the developed MOF on the wire is evaluated using polar formaldehyde gas and nonpolar cyclohexane vapor as hazardous model gas/vapor (GV). The key discovery highlights the pivotal role of functional compatibility between a GV and MOF in governing GV diffusivity through mesopores (<20 nm) within the MOF, as validated through an experimental analysis and theoretical calculations. In contrast, interparticle diffusivity through larger pores (>20 nm) remains unaffected, demonstrating the unique influence of nanoscale interactions. Semiempirical atomic simulations support the experimental results, revealing stronger interactions and more adsorption sites for compatible GV-MOF pairs. This study establishes a sustainable pathway for designing advanced GV adsorbents, emphasizing the importance of micro-/meso-diffusivity in a hierarchical porous structure to maximize the overall adsorption capacity. A proof-of-concept for a multipurpose GV adsorbent is conceived by weaving MOF wires with different functionalities to achieve the simultaneous removal of polar and nonpolar GVs.